JP2013134158A - Radiation intensity measuring method for radiation intensity measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation intensity measuring apparatus capable of monitoring intensity changes of light made incident on a light receiving part and capable of feeding back correction matched with changes of light intensity of measurement results.SOLUTION: The radiation intensity measuring apparatus includes a measurement device for measuring a component not caused by excitation of a photostimulable crystal of light measured by the light receiving part, analyzes influences of optical fiber deterioration and light bending loss, and uses the analyzed results as correction data. Further, time distributions of light intensities of both of light not caused by the excitation of the photostimulable crystal and light caused by the excitation of the photostimulable crystal are measured, and a change in the crystal structure of the photostimulable crystal is monitored from a change of the time distribution of the light caused by the excitation of the photostimulable crystal with respect to the time distribution of the light not caused by the excitation of the photostimulable crystal.

Description

  The present invention relates to a radiation intensity measuring apparatus and a radiation intensity measuring method for measuring radiation intensity, and more particularly to a radiation intensity measuring apparatus and a radiation intensity measuring method using an optically stimulated (OSL) crystal.

  When the photostimulable crystal is irradiated with radiation, electrons are excited and transition from the valence band to the conduction band. The electrons transitioning to the conduction band become metastable when trapped by lattice defects, so that the excited state is maintained. On the other hand, holes are generated in the valence band because electrons are lost. When the excited photostimulable crystal is irradiated with light of a specific wavelength, the electrons in the conduction band return to the valence band, and the electrons and holes combine to produce a light emission phenomenon. The emission intensity of this luminescence phenomenon depends on the amount of excited electrons, and the excitation by radiation irradiation is a stochastic event, so the number of excited electrons increases as the radiation dose increases. Therefore, by examining the emission intensity from the photostimulable crystal, the radiation dose applied to the photostimulable crystal can be determined. Moreover, since the radiation dose to the photostimulable crystal is determined by the radiation intensity and the irradiation time, the radiation intensity can be derived from the emission intensity and the irradiation time from the photostimulable crystal.

  Radiation-irradiated photostimulable crystal is irradiated with laser light through an optical fiber, causing the photostimulable crystal to emit light, and the generated light is transmitted through the same or another optical fiber, and the emission intensity is examined. Thus, it is possible to measure the radiation intensity at a position away from the photostimulable crystal. In addition, since no power source is required during the process of exciting the photostimulable crystal, it is not necessary to prepare a power source around the location where the photostimulable crystal is installed, and in places where it is difficult to install a power source or measuring device. It is possible to measure radiation intensity.

  As a technique for measuring a radiation intensity distribution using a photostimulable crystal, there is a radiation intensity measuring apparatus disclosed in Prior Literature 1. This device is a device in which a plurality of photostimulable crystals are arranged and the radiation intensity at each installation position is measured. In this device, the laser light from the laser light source is distributed by the light distribution device, so that the radiation intensity irradiated to multiple photostimulable crystals can be examined with a single measuring device including the laser light source and the light receiving unit. It is said.

  Such a technique is described, for example, in JP-A-11-23749.

JP 11-23749 A

  In radiation intensity measurement using a photostimulable crystal and an optical fiber, the photostimulable crystal and the optical fiber deteriorate. There are two causes of deterioration, one due to radiation irradiation and the other due to aging. When the deterioration occurs, the correlation between the light intensity obtained at the light receiving portion and the radiation intensity irradiated to the photostimulable crystal changes, so that correct radiation intensity measurement cannot be performed. Similarly, when the bending loss of light changes due to changes in the installation environment of the optical fiber, the correlation between the light intensity obtained at the light receiving part and the radiation intensity irradiated to the photostimulable crystal changes, so the correct radiation intensity measurement Can not be.

  In addition, when the control is performed at a position away via the optical fiber, it is difficult to directly observe the change of the photostimulable crystal because the change at the installation position of the photostimulable crystal cannot be observed directly. At this time, even if a physical change occurs in the photostimulable crystal, it cannot be noticed, and correct radiation intensity measurement cannot be performed.

  Furthermore, when using a plurality of photostimulable crystals as in the prior art, the bending loss of light occurs depending on the installation environment of the optical fiber, and the light intensity obtained at the light receiving part varies, so it is measured as the radiation intensity. The correlation of the light intensity varies depending on the position where the photoluminescent crystal is installed. This problem is not a problem at the initial stage by correcting each photoluminescent crystal when it is installed, but if there is a change in the environment of the installation site or the laying of the optical fiber during long-term use, Since the correction value is incorrect, correct radiation intensity measurement cannot be performed. Similarly, since the optical fiber is deteriorated at different timings and levels for each of the photostimulable crystals, the correction value becomes incorrect and correct radiation intensity measurement cannot be performed.

  Due to these causes, there has been a problem that reliability of the radiation intensity measuring device using the photostimulable crystal and the optical fiber is lowered when used for a long period of time or when installed at a plurality of locations.

  An object of the present invention is to provide a radiation intensity measuring device and a radiation intensity measuring method capable of changing a light emission intensity due to deterioration or environmental change.

  In order to achieve the above object, the present invention includes a measuring device that measures a component that is not caused by excitation of the photostimulable crystal in the light measured by the light receiving unit.

  The apparatus of the present invention can cope with changes in emission intensity due to deterioration and environmental changes.

The whole figure of a radiation intensity measuring device. The figure which shows another Example. The figure which shows another Example.

  Embodiments of the present invention will be described below with reference to the drawings.

  A radiation intensity measuring apparatus according to embodiment 1, which is a preferred embodiment of the present invention, will be described with reference to FIG.

Here, the basic concept of the present embodiment will be described.
The component not caused by excitation of the photostimulable crystal is caused by light scattering and reflection in the process from the light source to the light receiving part, and its intensity depends on optical fiber degradation and light bending loss. Therefore, by measuring these components, it is possible to monitor the effects of optical fiber degradation and light bending loss. In addition, the first light component obtained in the light receiving part is a light component not caused by excitation of the photostimulable crystal, or a mixed component of light caused by excitation of the photostimulable crystal and light caused by excitation of the photostimulable crystal. Become. In any case, the rise of the time distribution of the light intensity includes a light component not caused by excitation of the photostimulable crystal. The time difference between the rise time of light not caused by excitation of the photostimulable crystal and the time peak of light caused by excitation of the photostimulable crystal is usually constant, but the time difference changes due to the change in the structure of the photostimulable crystal. . Such a phenomenon occurs due to deterioration of the photostimulable crystal due to irradiation or physical change of the photostimulable crystal. Therefore, it is possible to monitor the change of the photostimulable crystal by measuring the time distribution of light not caused by excitation of the photostimulable crystal and the time distribution of light caused by excitation of the photostimulable crystal. The time difference mentioned here includes that the time width of light generation due to excitation of the photostimulable crystal becomes longer.

  The radiation intensity measuring device of Example 1 includes a photostimulable crystal 1, a laser light source 2, a light receiving unit 3, an amplifier 4, an optical analysis device 5, an excitation light measurement device 6, an excitation light analysis device 7, and a non-excitation light measurement device 8. , A non-excitation light analyzing device 9, an output optical fiber 10, and an input optical fiber 11.

  Electrons in the photostimulable crystal 1 are excited by irradiation. Laser light is incident on the excited photostimulable crystal 1 from the laser light source 2 through the input optical fiber 11. The laser light returns the electrons in the photostimulable crystal 1 to the ground state, and at that time, excitation light is emitted from the photostimulable crystal 1. The emitted excitation light enters the light receiving unit 3 through the output optical fiber 10 and is converted into an electric signal. On the other hand, a part of the component of the laser light is scattered and reflected by the input optical fiber 11, the photostimulable crystal 1, and the output optical fiber 10 in the process from the laser light source 2 to the light receiving unit 3, The light enters the light receiving unit 3 and is converted into an electric signal. Both the electrical signal based on the excitation light and the electrical signal not based on the excitation light are amplified by the amplifier 4 and are caused by the excitation of the photostimulable crystal 1 and the excitation of the photostimulable crystal 1 by the optical analyzer 5. It is divided into signals that do not. A signal resulting from the excitation of the photostimulable crystal 1 is measured by the excitation light measuring device 6, and the time distribution and the wave height distribution of the light intensity are analyzed by the excitation light analyzing device 7. Further, a signal not caused by excitation of the photostimulable crystal 1 is measured by the non-excitation light measuring device 8 and analyzed by the non-excitation light analyzing device 9.

  When the radiation intensity measuring apparatus of Example 1 is operated, measurement data of light not caused by excitation of the photostimulable crystal 1 is acquired and analyzed in advance, and the data and the photostimulable crystal 1 at the time of actual measurement are analyzed. Compare with measurement data of light not caused by excitation. When there is an increase in light attenuation due to deterioration or bending loss of light in the optical fiber, the intensity of light not caused by excitation of the photostimulable crystal 1 and light caused by excitation of the photostimulable crystal 1 are increased. Attenuates. At this time, the amount of light attenuation caused by the excitation of the photostimulable crystal 1 can be estimated from the amount of light attenuation not caused by the excitation of the photostimulable crystal 1. Data of light components not caused by excitation of the photostimulable crystal 1 obtained in advance may be stored in a database and incorporated in the non-excitation light analyzing device 9. Changes in the environment include increase / decrease in light bending loss due to changes in the laying condition of the output optical fiber 10 or the input optical fiber 11, radiation deterioration of the output optical fiber 10 or the input optical fiber 11, and aging. Deterioration is considered.

  Moreover, even if the data of the light component not resulting from the excitation of the photostimulable crystal 1 has not been acquired in advance, by comparing the signals not caused by the excitation of the photostimulable crystal 1 for each measurement, It is possible to monitor relative environmental changes.

  Further, by calculating the increase / decrease of the measured value due to the change of the environment from the signal not caused by the excitation of the photostimulable crystal 1 and correcting the measured value of the signal caused by the excitation of the photostimulable crystal 1, Radiation intensity measurement can be performed without depending on the change of. This correction may be automatically performed by feeding back the result of the non-excitation light analysis device 9 to the excitation light measurement device 6.

  A radiation intensity measuring apparatus according to embodiment 2, which is a preferred embodiment of the present invention, will be described with reference to FIG.

  The radiation intensity measuring device of Example 2 includes a photostimulable crystal 1, a laser light source 2, a light receiving unit 3, an amplifier 4, an optical analyzer 5, an excitation light measuring device 6, an excitation light analyzing device 7, and a non-excitation light measuring device 8. , A non-excitation light analyzing device 9, an output optical fiber 10, and an input optical fiber 11.

  The process for analyzing separately the light caused by excitation of the photostimulable crystal 1 and the light not caused by the excitation is the same as in the first embodiment.

  The radiation intensity measuring apparatus according to the second embodiment handles a signal that is not caused by excitation of the photostimulable crystal 1 as a timing signal. The timing difference between the component of the laser light emitted from the laser light source 2 and the component that enters the light receiving unit 3 at the shortest and the component that enters the light receiving unit 3 at the shortest of the signal resulting from excitation of the photostimulable crystal 1 is as follows. The same as long as the configuration of the apparatus is not changed. Therefore, by measuring the time distribution of the light intensity of the component resulting from the excitation of the photoluminescent crystal 1 using the rise time of the signal not resulting from the excitation of the photoluminescent crystal 1 as a reference timing, The change in the time distribution of the light intensity of the component due to the excitation of the crystalline 1 can be observed.

  In FIG. 2, the light intensity distribution (light intensity time distribution) 101 when there is no change in the photoluminescent crystal 1 and the light intensity distribution (time distribution of light intensity) when the photoluminescent crystal 1 is changed. ) 102. When the photoluminescent crystal 1 is changed, the light intensity distribution with respect to the time is emitted at a later time. The term “slow” here means that the rise timing is delayed or the emission time of the excitation light is lengthened. Moreover, the change of the said photostimulable crystal 1 said here is deterioration of the said photostimulable crystal 1, and a physical change. Therefore, by analyzing the change in the time distribution of the light intensity caused by the excitation of the photostimulable crystal 1 based on the rise time of the time distribution caused by the light not caused by the excitation of the photoluminescent crystal 1, The deterioration and physical change of the exhaustive crystal 1 can be monitored. At this time, the non-excitation light analyzing device 9 analyzes the rise time of the signal not caused by the excitation of the photostimulable crystal 1, and the excitation light analyzing device 7 uses the excitation light analyzing device 7 to analyze the photostimulable crystal 1. The time distribution of the signal due to excitation is analyzed.

  Further, the light intensity of the photostimulable crystal 1 decreases with the change of the time distribution of the light intensity emitted from the excited photostimulable crystal 1. Therefore, the excitation light analyzing / calculating device 7 may have a function of calculating a correction value of the light intensity according to a change in the time distribution of the light intensity and correcting the count value in the exciting light analyzing / calculating device 7.

  A radiation intensity measuring apparatus according to embodiment 3, which is a preferred embodiment of the present invention, will be described with reference to FIG.

  The radiation intensity measuring apparatus of Example 3 includes a plurality of photostimulable crystals 1, a laser light source 2, a light receiving unit 3, an amplifier 4, an optical analyzer 5, an excitation light measurement apparatus 6, an excitation light analysis apparatus 7, and non-excitation light measurement. Device 8, non-pumping light analysis device 9, a plurality of output optical fibers 10, a plurality of input optical fibers 11, an input light distribution device 21, an output light distribution device 22, a non-pumping light calculation device 31, a radiation intensity calculation The device 32 is configured.

  The process for analyzing separately the light caused by excitation of the photostimulable crystal 1 and the light not caused by the excitation is the same as in the first embodiment.

  The radiation intensity measuring apparatus according to the third embodiment is configured to measure the radiation intensity at a plurality of locations. The position where the radiation intensity is measured is determined by the installation position of the photostimulable crystal 1. In the present embodiment, a common material other than the photostimulable crystal 1 is used except for the photostimulable crystal 1, the output optical fiber 10, and the input optical fiber 11. Laser light emitted from the laser light source 2 is sequentially transmitted to the respective photostimulable crystals 1 by the input light distribution device 21 via the respective input optical fibers 11. The light incident on the light receiving unit 3 is sequentially transmitted by the output light distribution device 22 via each output optical fiber 10 for each photoluminescent crystal 1. Since the two light distribution devices have a predetermined channel for each of the photostimulable crystals 1, the channel of one of the light distribution devices is switched so that the channel of the other light distribution device is simultaneously switched. Has been. If the light is incident on the common light receiving unit 3 and does not affect the other photostimulable crystal 1, or if the influence is negligible, the output light distribution device 22 may not be provided. good.

  When a plurality of photostimulable crystals 1 are installed as in this embodiment, the difference in output sensitivity with respect to the input depends on the installation method when each photostimulable crystal 1 is installed and the environment after installation. May occur. In order to correct this sensitivity difference, signals that are not caused by excitation of all the photostimulable crystals 1 are compared, and a correction value is calculated by the non-excitation light calculation device 31 so that the signal intensity of the non-excitation light becomes equal. The radiation intensity calculation device 32 corrects the measurement values resulting from the excitation of all the photostimulable crystals 1. The sensitivity difference referred to here is light transmission loss including light bending loss and optical fiber deterioration.

DESCRIPTION OF SYMBOLS 1 Photoluminescent crystal 2 Laser light source 3 Light-receiving part 4 Amplifier 5 Optical analyzer 6 Excitation light measurement device 7 Excitation light analysis device 8 Non-excitation light measurement device 9 Non-excitation light analysis device 10 Output optical fiber 11 Input optical fiber 21 Input light distribution device 22 Output light distribution device 31 Non-pumping light calculation device 32 Radiation intensity calculation devices 101 and 102 Light intensity distribution

Claims (13)

  A light receiving unit for measuring light emitted from the photostimulable crystal, wherein the photoluminescent crystal is irradiated with laser light from a laser light source, and transmitted from the light receiving unit. Radiation intensity measurement apparatus comprising a measurement apparatus for measuring light emitted from a photostimulable crystal, comprising a measurement apparatus for measuring a light component not caused by excitation of the photostimulable crystal. apparatus.   The radiation intensity measuring apparatus according to claim 1, further comprising an amplifier that amplifies a signal corresponding to an output of light obtained by the light receiving unit.   2. The radiation intensity measuring apparatus according to claim 1, wherein the laser light is applied to the photostimulable crystal through an optical fiber, and light emitted from the photostimulable crystal is applied to the light receiving unit through the optical fiber. Radiation intensity measurement characterized by an analysis device that analyzes the change in light intensity due to optical fiber degradation and light bending loss from signals transmitted and not caused by excitation of the photostimulable crystal apparatus.   4. The radiation intensity measuring apparatus according to claim 3, wherein the apparatus for analyzing the signal caused by excitation of the photostimulable crystal is corrected by a correction value calculated from the analysis of the signal not caused by excitation of the photostimulable crystal. A radiation intensity measuring device having a function.   The radiation intensity measuring apparatus according to claim 1, further comprising an analysis device for analyzing a time distribution of light not caused by excitation of the photostimulable crystal and light caused by excitation of the photostimulable crystal. Radiation intensity measuring device.   6. The radiation intensity measuring apparatus according to claim 5, wherein a time distribution of light not caused by excitation of the photostimulable crystal is used to change a time spread in which light caused by excitation of the photostimulable crystal reaches the light receiving part. A radiation intensity measuring device comprising an analyzing device for analysis.   6. The radiation intensity measuring apparatus according to claim 5, wherein the time delay of the light due to excitation of the photostimulable crystal reaching the light receiving part is analyzed using the time distribution of light not caused by excitation of the photostimulable crystal. A radiation intensity measuring device comprising an analyzing device.   8. The radiation intensity measuring apparatus according to claim 5, wherein an apparatus for analyzing a signal caused by excitation of a photostimulable crystal is calculated from a change in time distribution of light caused by excitation of the photostimulable crystal. A radiation intensity measuring device having a function corrected by the correction value.   The radiation intensity measuring apparatus according to claim 1, wherein BaFBr is used as the photostimulable crystal. The radiation intensity measuring apparatus according to claim 1, wherein Al ₂ O ₃ is used as the photostimulable crystal.   The radiation intensity measuring apparatus according to any one of claims 1 to 9, wherein a support plate coated with a photostimulable substance is used instead of the photostimulable crystal.   A plurality of photostimulable crystals, a laser light source, a light distribution device that distributes light from the laser light source, a plurality of optical fibers that transmit the distributed light to the plurality of photostimulable crystals, and the photostimulable crystal A common light receiving unit for measuring light emitted from the crystalline crystal and transmitted through the optical fiber, a measuring device for measuring the light from the light receiving unit, and a light component not caused by excitation of the photostimulable crystal A radiation intensity measuring device having a measuring device for measuring, comprising: an arithmetic device for correcting a sensitivity difference between photostimulable crystals from a difference in light intensity not caused by excitation of the photostimulable crystal. Radiation intensity measuring device.   The light emitted from the photostimulable crystal is measured by the light receiving portion, the light emitted from the light stimulable crystal from the light receiving portion is measured by the measuring device, and is not caused by the excitation of the light analyzing device and the photostimulable crystal. A radiation intensity measurement method that measures light components.